1. Field of the Invention
This invention relates generally to devices for smoothing a coating of mortar or similar material such as plastic lining to the interior walls of pipes, conduits and the like to insure a smooth uniform coating at all peripheral interior wall portions of the pipes or conduits.
2. Description of the Prior Art
Devices for applying a lining of mortar or like plastic material to the interiors of pipes and the like are well known and generally comprise a machine which travels on rollers through the pipes to be lined, distributing a coating of the lining material.
Attached to this machine and directly following it, by being pulled by same, is what is known in the art as a "drag" trowel, which is the subject of this invention. Most such "drag" trowels consist of a frusto-conical type body which is adapted to be drawn through a pipe by the coating applying machine, thus troweling the newly applied coating into a smooth internal surface. The large ends of such trowels generally have some means to establish that it is resiliently expandable and contractible in diameter and which end trails the smaller diameter end or mounting end when drawn by the coating machine through the pipe.
A primary problem of the prior art is the opportunity for mortar or other material used to line pipes with to fall into the troweling device and clog same. Although many devices of this type have springs and other means to keep the plate members from coming apart at the large end so that mortar will not enter and clog the same, mortar could be thrown off the coating machine and enter into the small end of many other of these types of devices. None of the prior art includes a completely closed body as does the one in this invention.
Where the prior art examples have frames and/or pivot points on which the trowel plate members are mounted, many of these pivots and frames are exposed and easily subject to clogging or breaking from falling mortar or small stones which may have been mixed into the mortar. This, in turn, could render the trowel unuseable while in use.
Another problem with the prior art is the use of small springs, a plurality of which may be attached directly to the plate members. These spring members keep the plate members together and aid in the compressibility of the trowel but there is a possibility of the trowel being dented along the edges and in the places where there is no spring member. These small dents could affect the action of the trowel.
Another problem could be encountered by the use of these many spring members on the trowel. As the trowel is used, some of these spring members will invariably stretch more than the others and after being used, some of the plate members will have less troweling pressure as a result of these weaker springs. This, in turn affects the radial troweling effect of the troweling device.
A further problem is that in many of the prior art patents the trowels are attached to the mortar applying machine or drawn through the pipes by a plurality of attaching rods. Should one of these rods break or even get bent, it would throw the trowel on an uneven slant and ruin the troweling effect in the pipe.
Known prior art U.S. Pat. Nos. relating to this invention are as follows:
A. G. Perkins--3,619,873--July 31, 1969 PA0 W. E. Perkins--3,188,710--Feb. 3, 1964 PA0 J. T. Barton--3,368,253--Nov. 22, 1965 PA0 J. T. Barton--3,384,940--May 28, 1968
In all of these prior art patents all of the devices have an open small leading end and are subject to possible clogging from the mortar or other lining material falling into the device.
They also all include a plurality of small springs which are mounted onto the plate members between their respective overlaps and which are subject to wearing out or breaking and causing uneven pressure of the plate members against the pipe. The plate members are also subject to dents in the places between where the springs are located if the springs can't absorb shocks quickly.
A plurality of attaching rods are seen in U.S. Pat. Nos. 3,619,873 and 3,188,710. As stated before should one of these rods get bent or be broken the troweling effect of the trowel could be uneven.
In U.S. Pat. Nos. 3,619,873; 3,188,710 and 3,384,940 the mounting points for the plate members are exposed and thus more subject to possible breakage or clogging which would affect the proper working ability of the trowel.
None of these prior art devices offers the new and unique features of the invention disclosed herein.